October 13, 2022: Topaz Arcturus nears its heliacal rising. Find it by following the Big Dipper’s handle. Mars appears near the Crab Nebula through a binocular.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:01 a.m. CDT; Sunset, 6:12 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Before sunrise, begin looking for the bright star Arcturus. It appears low in the east-northeast to the unaided eye during the next week at 45 minutes before sunrise – its first morning appearance or heliacal rising.
Arcturus is the brightest star in the northern half of the sky, that is north of the celestial equator, the line above Earth’s equator. It is the third brightest in the skies of Earth following Sirius and Canopus – that is not visible from mid-northern latitudes.
It is far enough north that it is visible in the western sky after sundown and in the east-northeast before day break.
The celestial cue that Arcturus is nearing its heliacal rising is the position of the Big Dipper. At this season, it stands on its handle in the northeast during morning twilight. The curving handle points toward the east-northeast horizon where Arcturus rises.
Each morning the dipper is slightly higher and the arcing handle points a little higher in the sky. Soon the star becomes visible through a binocular. Then it appears high enough to be seen to the unaided eye as it slowly disappears into the growing glow of the approaching dawn. Each morning it’s higher in the eastern sky.
From Chicago’s latitude, the star’s disappearance from the evening sky begins at about 45 minutes after sunset starting November 15th. The star is low in the west-northwest and visible without a binocular. Then with a lower altitude – height above the horizon – topaz Arcturus is only visible through a binocular. Then it is below the horizon at this time interval.
During mid-November, Arcturus is about one-third of the way up in the east at morning’s mid-twilight. Unlike other stars farther southward in the sky, it makes its first morning appearance before it leaves the evening sky. The same effect occurs with Vega, Deneb, Capella, and other northern stars.
Interestingly, the same effect occurs for stars for our southern hemisphere readers. In particular, Sirius, is still in the evening sky, when it makes its helical rising. From about latitude 30° South, Sirius is at its heliacal rising about June 22nd, but the star sets around two hours after sunset. It doesn’t disappear from the evening sky until approximately June 11.
With the westward migration of the constellations, Arcturus makes its first appearance in the east-northeast after sunset during March each year.
Here is today’s planet forecast:
Slightly brighter than Mars and beginning its retreat into deeper morning twilight, Mercury continues to appear in the eastern sky at mid-twilight, about 45 minutes before sunup. The planet brightens as it races toward the far ends of its orbit on the far side of the sun.
This morning the planet rises 88 minutes before daybreak. It loses three to four minutes of rising time each morning during the next week. This means that at this time interval before sunrise, it is lower in the sky but brighter.
The planet’s appearance is the best of the year. It is less than 8° up in the eastern sky at this time. It’s easy to see if there’s a clear horizon, free from clouds and local obstructions. A view from an elevated structure or hilltop helps to see Mercury.
The bright waning gibbous moon, 87% illuminated, is high in the west-southwest. It is between the Pleiades star cluster and the Hyades cluster. The bright moon’s light washes out the dimmer stars that are shown on the accompanying chart. They can be found through a binocular.
The Pleiades cluster is over 3° to the right of the lunar orb and they easily fit into the same binocular field of view.
Even with the moon’s brightness, try to see Mars, the Crab Nebula (M1 on the chart), and Zeta Tauri in the same binocular. Mars is 2.4° to the upper right of the star and the nebula is midway between them. The planet and the star are easy to see. The Crab is the challenge. Mars is too far away from M1 to see them in the same telescopic field of view.
The nebula is the remains of a star that burst open in a blaze of light in the year 1054. It was visible in the sky for nearly two years before it faded from view, leaving a haze of expanding gases and a rapidly rotating neutron star at its center.
The Crab Nebula is a challenge to see in urban and suburban settings with many outdoor lights. Moonlight adds to that challenge. It appears as a small oval haze in the binocular field, perhaps slightly brighter than the lighted sky.
The Crab is the first entry on a list of fuzzy looking objects that 18th Century comet hunter Charles Messier did not want to confuse with the fuzzy or “hairy” stars that he pursued. Seeing the over 100 objects on Messier’s list is a goal of many backyard sky watchers. On moonless nights near the vernal equinox all of them are visible during one setting from the end of evening twilight to the beginning of morning twilight. Like-thinking sky watchers use this night to complete a “Messier Marathon.” Others choose to complete their observations during each season.
Venus is about a week from its solar conjunction and move into the evening sky as the Evening Star. The planet only 13 minutes before sunrise.
Jupiter and Saturn are in the eastern sky after sunset. That “bright star” in the east-southeast is Jupiter, the brightest star in the sky this evening. Saturn is about one-third of the way up in the south-southeast.
By three hours after sunset is low in the east-northeast. Mars soon follows the lunar orb across the horizon.
As the midnight hour approaches, the three bright outer planets (BOPs) – Mars, Jupiter, and Saturn – and the moon are hung across an arc from the eastern sky to the southwest.
- 2023, December 19: A Scorpion Fumble, Moon MidwayDecember 19, 2023: Before sunrise, Venus appears below the Scorpion’s claws. After sundown, the moon is nearly midway from Saturn to Jupiter.
- 2023, December 18: Pinched VenusDecember 18, 2023: Look for Venus between the Scorpion’s claws in the southeast before sunrise. The thick crescent moon is in the evening sky with Jupiter and Saturn.
- 2023, December 17: Celestial PairsDecember 17, 2023: Before sunrise, Venus passes Zubenelgenubi, a planet-star conjunction. After sundown, Saturn and crescent moon are paired, a planet-moon conjunction.
- 2023, December 16: Venus Clawed, Evening Crescent Nears SaturnDecember 16, 2023: Before daybreak, Venus is above the Scorpion’s southern claw. After nightfall, the crescent moon nears Saturn.
- 2023, December 15: Brilliant Morning Star, Evening Lunar CrescentDecember 15, 2023: Before sunrise, brilliant Venus approaches Zubenelgenubi, the Scorpion’s southern claw. The crescent moon returns to the western evening sky.